The present invention relates to a method and apparatus for diagnosing the condition of oil-wetted parts subject to wear, such as internal combustion engines, bearings, valves, and the like.
Techniques are known for analyzing used oils to diagnose the condition of oil-wetted parts subject to wear, particularly internal combustion engines. The commonly used technique is to extract a specimen of the oil from the oil-wetted part and to analyse it, for example by spectrometric analysis, to determine the composition of the particles in the oil specimen; this provides an indication of the parts from which the particles were derived and therefore the parts subject to the wear. A serious drawback of the known technique, however, is that the procedure merely identifies the total quantity of each of the chemical elements in the specimen contributed by an alloy which is contained in the specimen. Therefore it is difficult to identify the part suffering the major wear, or to determine its rate of wear, particularly when the part includes a number of alloys of similar constituents. Thus if the system being diagnosed includes two or more alloys with similar constituents, with one part being of large size and exhibiting a normal rate of wear, and another part being of small size and exhibiting an abnormally high rate of wear, it is difficult or impossible to determine whether the system as a whole is exhibiting an abnormally high rate of wear in any of its parts, because of the "shielding" influence one element of one part exhibits on the same element of another part.
Another drawback in the conventional technique is that in order to make a life prediction of the part, at least two tests at different time periods of use are required, because the life of the part depends on the "rate" of wear.